This one really has me stumped. You can play for a bit and then the sound just stops. All new caps, new pot on the speech board as well as volume control at the door. Resoldered all the connectors. I even replaced the voltage regulator on the sound board. I'm getting a nice 12 volts at the 12 volt test point and 5.04 at the 5 volt test point. When the sound dies it will still make the speaker hum if you crank the volume, so it's not the speaker which is brand new as well. The machine was doing this before I touched it and none of the things I have done have fixed it. Turn it off and back on, start a game and there is sound. Is it the amp?